Light Sound and Waves

Seeing polarised light

Stories from Physics for 11-14 14-16 IOP RESOURCES

Unlike the animals described above, humans are largely polarisation-blind. However, some individuals may be able to perceive a polarisation effect known as Haidinger’s brush.

This appears as a tiny, yellowish figure-of-eight-shaped image about 3° in longitudinal diameter that may be seen in highly polarised light. It is suggested that the effect is most easily seen at the zenith of a clear sky, near sunset and sunrise. After a couple of minutes of observing, the sky may take on a marbled appearance and the brush should appear as a subtle mark against the sky.

Some people find the effect easier to observe than others. It can also be seen by observing a computer screen through a polarising filter for a couple of seconds and then quickly rotating the polaroid. The effect arises because pigments in the macula of the retina have a radial arrangement and linearly polarised light is absorbed more strongly in some parts of the pigments than others, causing a visible effect when the direction of polarisation of light is suddenly changed.


IOP DOMAINS Physics CPD programme

Energy CPD videos

Our new set of videos gives teachers and coaches of physics a preview of the training we offer ahead of this term's live support sessions.

Find out more